[Yaesu] FT-990 frequency stability

[Jim Barber]

Harry,

>My 990 has started to drift (more loke a wobble) a few Hz, most noticeable on 24 and 18, but then, that's where I spend most of my time. It seems to occur after switching bands, changes a little on both Tx and Rx, and then stabilizes. The readout does NOT change. It also seems to be intermittent, just to make it more impossible to pinpoint. Comments??
>Harry N2ERN

I don't have any particular experience with the 990, but the 
first place I'd look in any Japanese radio is the cheap plastic
trimmer caps for the oscillators. (master and other) I've seen
quite a number of them get dirty/stuck with age, and cause strange
problems with both PLL's and DDS's.  Sometimes just turning the cap
through its range a few times then resetting it to the correct
frequency will "fix" the problem.  Loose-coupling a general coverage
SSB receiver tuned to the oscillator frequency (with a few turns of
wire) will identify if a particular one is wobbling.  The ear is a 
pretty good troubleshooting tool. :-)

My .02, 
Jim, N7CXI